1. Field of the Invention
The present invention relates to a projection-type projector, and particularly, relates to an unauthorized use preventing system of a projection-type projector, which prevents unauthorized use of the projection-type projector.
2. Description of the Background Art
As an instrument for use in presentation, a projection-type projector is communally used in a frequent manner at a place where many people gather, such as a conference room, a field of education, which includes a school or the like, and a training facility. At such a place, and particularly, in a wide room, it takes time to move the projection-type projector from a storage place thereof and fix the projection-type projector to a dedicated fixing device provided on a ceiling or a wall every time when the projection-type projector is used, and accordingly, in general, it is frequent that the projection-type projector is used while being left fixed to the ceiling or the wall.
Meanwhile, it is frequent that a small and lightweight projection-type projector is shared by a plurality of persons in such manners that the projection-type projector is taken to a business trip destination, is carried to a plurality of conference rooms, and so on. In such use, it is rare that the projection-type projector is fixed to the ceiling or the wall, and it is general that the projection-type projector is used while being mounted on a desk or a base.
In any of the cases described above, it is highly possible that the projection-type projector, which is relatively expensive, may be stolen during a period while being left. Therefore, measures for preventing unauthorized use of the projection-type projector or preventing theft thereof, which include restriction of use, the restriction being implemented by setting a password, have been adopted. However, convenience for users has been lost since the password must be inputted every time when the projection-type projector is used, for example, every time when a power supply thereof is turned on.
For this problem, for example, a projection-type video display device of Japanese Patent No. 4826130 (Patent Literature 1) detects a usage thereof at the time when a power supply thereof is turned on, and compares the detected usage with a usage thereof at the last time, and thus prevents the convenience from being lost by requiring input of a password only at the time when the usage is changed.
In the projection-type video display device of Patent Literature 1, as such usages, there are mentioned: an installation orientation of the device; an installation direction of the device; an installation place of the device; an input state to an input terminal of the device; a fixation state of the device; and a focus/zoom setting state of lenses. Then, at the time of having detected that one or a plurality of these usages are changed, the projection-type video display device determines that there is a possibility that the projection-type video display device may be unauthorizedly used, and requires the input of the password. Then, when the password does not coincide with one stored in the projection-type video display device, the projection-type video display device restricts the use thereof, or emits an alarm sound.
Moreover, a display device of Japanese Patent Application Laid-Open No. 2008-233831 (Patent Literature 2) includes a GPS receiver and a memory that stores a position detected by the GPS receiver. Then, this display device compares a current position thereof, which is measured by the GPS receiver, with a position thereof, at which the display device is used at the last time, stored in the memory, determines that there is a possibility that the display device may be unauthorizedly used if the two positions are spaced apart from each other at a fixed distance or more, and requires the input of the password. Then, in the case where the password does not coincide with one stored in the display device, the display devices restricts the use thereof, or emits an alarm sound.
However, even if such a theft preventing device according to Patent Literature 1 is provided, in the small and lightweight projection-type projector, which is frequently used after being moved, the input of the password is required every time when the projection-type projector is moved, and accordingly, improvement of the convenience is limited. Moreover, when input characters, numbers and the like of the password are reduced in order to suppress a decrease of the convenience, there has been a problem that the password is known to another person after the projection-type projector is stolen.
Moreover, in Patent Literature 1, it is mentioned that, in the projection-type video display device, the input of the password can be replaced by pushing of a release button of a remote controller (remote control) provided with a function to send out a signal for releasing the unauthorized use preventing system. The remote control as described above is stored in a place different from that of the projection-type video display device, the remote control is taken out only in the event of using the projection-type video display device, and the password is released by pushing the release button of the remote control, and if so, then it becomes possible to save the need for inputting the password; however, it becomes essential to carry the remote control upon turn-on for which the input of the password is required.
Moreover, in a body of the projection-type video display device (projection-type projector), operation buttons are usually provided, and the projection-type video display device is configured to be operable without the remote control; however, there has been a problem that it becomes necessary to input the password at an operation time by the operation buttons. Moreover, such a problem is not solved that, once the password is known to another person, the projection-type video display device is used without any difficulty thereon and thereafter.
In a similar way, even if the theft preventing device according to Patent Literature 2 is provided, there has been a problem that, once the password is known to another person, the display device is used without any difficulty thereon and thereafter.